It is the first big overhaul since 1998, and could be the first glimpse of what astronauts look like when they return to the surface of the Moon - or head to Mars.

Nasa said one of the key differences was that the new suit has a one-piece design, into which the wearer crawls in through a hole in the back, as opposed to the trousers-top-helmet version currently in use on the International Space Station.

"One of the big differences is the rear-entry design," said Nasa's Amy Ross in a video interview.

"So the shuttle EMU splits at the waist and you put pants on and you put the top on separately and they connect in the middle. Whereas with this suit, the subject crawls in through the back, and then we just shut the door."

It is also thought to be less prone to causing injuries.

Nasa will continue testing the new suits, but it could be used as soon as 2015.